Method iter

basex-core/src/main/java/org/basex/query/func/fn/FnTrunk.java:21–65

(final QueryContext qc)

 */
public final class FnTrunk extends StandardFunc {
  @Override
  public Iter iter(final QueryContext qc) throws QueryException {
    // retrieve and decrement iterator size
    final Iter input = arg(0).iter(qc);
    final long size = input.size();

    // return empty iterator if iterator yields 0 or 1 items, or if result is an empty sequence
    if(size == 0 || size == 1) return Empty.ITER;

    // check if iterator is value-based
    if(input.valueIter()) return input.value(qc, null).subsequence(0, size - 1, qc).iter();

    // return optimized iterator if result size is known
    if(size != -1) return new Iter() {
      int c;

      @Override
      public Item next() throws QueryException {
        return ++c < size ? qc.next(input) : null;
      }
      @Override
      public Item get(final long i) throws QueryException {
        return input.get(i);
      }
      @Override
      public long size() {
        return size - 1;
      }
    };

    // otherwise, return standard iterator
    return new Iter() {
      Item last = input.next();

      @Override
      public Item next() throws QueryException {
        final Item item = last;
        if(item != null) {
          last = input.next();
          if(last == null) return null;
        }
        return item;
      }
    };
  }

  @Override
  public Value value(final QueryContext qc) throws QueryException {